A power-driven ski is relatively a new comer to the field of motorized winter sports. It provides unique and new ways of enjoying the snow covered outdoors, and it calls for some new and unique mechanisms to make "power-skiing" possible, convenient and safe.
As has been explained in Royce H. Husted's U.S. Pat. No. 3,853,192, issued on Dec. 10, 1974, which is herein incorporated by reference, a power-driven ski provides the skier, on one hand, with some challenges of down-hill skiing such as holding balance, steering and braking by body and skis manipulations, without being limited to a "one-way" skiing on an often crowded ski hill equipped with ski lifts, and, on the other hand, a power-driven ski provides the skier with the excitement of controlling his own propelling power, coupled with the freedom to roam over the snow-covered outdoors up or down hills, and especially over flat land as a snowmobile does, without imposing as large penalties of costs (purchasing & operating) and transportation.
At the same time, since power-skiing incorporates the fun of skiing and of snowmobiling into one sport, it also imposes on the power-skier the "chores" of skiing and of controlling the power-driven ski's engine power output, simultaneously.
Controlling the engine power, which in the case of an internal combustion engine is usually done in the form of varying the carburetor's throttle opening, poses unique problems, especially when the engine is mounted directly on the ski, as suggested in Husted's U.S. Pat. No. 3,853,192, column 2, lines 67 and 68.
While skiing, the feet are preoccupied and, any control functions have to be carried out by the hands. However, the hands are also partially preoccupied by the ski poles and, in addition, they are commonly used as "counter-weights" which the skier may throw upwards or sideways to maintain his balance. For example, commonly, when starting to power-ski, the skier may be thrusted forward by the power-driven ski, and attempt to maintain his balance by throwing his hands upwards above his head (as shown in FIG. 1 in a solid line). In contrast, when climbing a steep hill, the skier may be bending forward (note FIG. 1 in a phantom line) at which position his hands are in the vicinity of his boots and the power-driven ski's engine. The various positions and actions of the hands lead us back to note some of the unique problems that the throttle control has to accomodate; since, as mentioned, it must be hand operated, it has to follow the hand through all its gyrations and movements while the skier fights for his balance and, at the same time, the throttle control has to continuously transmit a steady signal to the engine. The throttle control must, therefore, be responsive to the relatively weak signal input and, to transmit this signal accurately and smoothly. (The importance of smooth and accurate throttle control can be visualised in the light of the above discussion, since it effects the smoothness and accuracy of the forward thrust generated by the power-driven ski, which effects the skier's ability to maintain balance).
In addition, the skier's hand may be either up above his head or, at the vicinity of his boot, i.e. it may be as far as ten feet from the engine or, as close as one foot, respectively. It is important that, while the hand is near the boot (and at all other times), no part of the throttle control is free to drag on the ground, as it may be damaged by the ski, interfere with the skier and cause his loss of balance. Further, the throttle control may be subjected to being sharply bent, twisted, as well as being exposed to snow, icing etc.
A second engine control function that should be provided at the skier's finger tips is the ability to shut off the engine. This should be done, for general safety considerations, and specifically for a case in which the throttle became stuck in an open position, or for a case in which the skier fell or, a case combining the two mishaps when the skier fell and the throttle became stuck. (It may be noted that such combined mishap is not as rare as one may assume since, on one hand, a wide open frozen throttle would often cause the skier's fall and, on the other hand, when a skier falls he may damage the mechanism and cause the throttle to be stuck in the open position).